Alexander’s denial came in the form of a two-page letter to Sen. Bernie Sanders (I-Vt.), according to USA Today. Sanders has been pressing the NSA chief for answers on the subject for weeks.

“Nothing NSA does can fairly be characterized as ‘spying on members of Congress or other American elected officials,’” Alexander wrote. The general’s letter was dated Friday and released Tuesday.

Sanders wasn’t satisfied with Alexander’s response, as it doesn’t rule out the possibility that lawmakers’ metadata could get swept up in broader surveillance scoops.

“The NSA is collecting enormous amounts of information,” said Sanders in a statement. “In my view, the information collected by the NSA has the potential to give an unscrupulous administration enormous power over elected officials.”

The NSA can request metadata — information such as a caller’s phone number and call history — when a phone number is “reasonably suspected” of being tied to a foreign terrorist group. However, privacy rights groups have argued the NSA’s powers to collect metadata have gone too far, as the agency has admitted it can look at data “two or three hops” from a number believed to be tied to a terrorist group.